Deep subterrestrial bioweathering of fossil organic matter and organic carbon redistribution of Kupferschiefer black shale – detection and identification of long-term bacterial processes in the mines

The weathered organic-rich subterrestrial Kupferschiefer black shale was detected in three underground copper mines and examined for description of long-term bacterial processes. The diversity of bacterial communities inhabiting the weathered black shale was estimated and the bacterial enzymes potentially responsible for the weathering of primary fossil organic matter were identified. Biological studies were completed with the physico- and geochemical characteristics of the weathered rock and identification of organic compounds produced by bacteria.Lithobiontic bacterial communities inhabiting the weathered black shale were represented by 25 phylogenetic classes and were dominated by ?-Proteobacteria, Bacilli and Actinobacteria. Bioweathering of fossil organic matter by bacteria in the deep underground system of mines has been demonstrated. The enzymes (e.g. oxygenases, laccases, and dehydrogenases) involved in the oxidative degradation of primary organic compounds included in the fossil organic matter of the black shale (e.g., long-chain aliphatic and polycyclic aromatic hydrocarbons) were identified. The biooxidation of bitumens, as well as the change of kerogen type and its hydrocarbon potential were shown. The redistribution of primary fossil organic carbon and the presence of secondary oxidized organic compounds (e.g. carboxylic acids, monohydroxy alcohols, diols, aldehydes, ketones and esters) in the weathered black shales was confirmed.